Fix for #2083 to release ack pending when messages expire or hit max redeliveries.

Signed-off-by: Derek Collison <derek@nats.io>

server/consumer.go

@@ -2916,10 +2916,22 @@ func (o *consumer) setInitialPending() {
 func (o *consumer) decStreamPending(sseq uint64, subj string) {
 	o.mu.Lock()
 	// Ignore if we have already seen this one.
-	if sseq >= o.sseq && o.sgap > 0 && o.isFilteredMatch(subj) && o.sgap > 0 {
+	if sseq >= o.sseq && o.sgap > 0 && o.isFilteredMatch(subj) {
 		o.sgap--
 	}
+	// Check if this message was pending.
+	p, wasPending := o.pending[sseq]
+	var rdc uint64 = 1
+	if o.rdc != nil {
+		rdc = o.rdc[sseq]
+	}
 	o.mu.Unlock()
+
+	// If it was pending process it like an ack.
+	// TODO(dlc) - we could do a term here instead with a reason to generate the advisory.
+	if wasPending {
+		o.processAckMsg(sseq, p.Sequence, rdc, false)
+	}
 }
 
 func (o *consumer) account() *Account {

server/jetstream_cluster_test.go

@@ -5303,6 +5303,118 @@ func TestJetStreamClusterAccountLoadFailure(t *testing.T) {
 	}
 }
 
+func TestJetStreamClusterAckPendingWithExpired(t *testing.T) {
+	c := createJetStreamClusterExplicit(t, "R3", 3)
+	defer c.shutdown()
+
+	// Client based API
+	nc, js := jsClientConnect(t, c.randomServer())
+	defer nc.Close()
+
+	_, err := js.AddStream(&nats.StreamConfig{
+		Name:     "TEST",
+		Subjects: []string{"foo", "bar"},
+		Replicas: 3,
+		MaxAge:   200 * time.Millisecond,
+	})
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	// Send in 100 messages.
+	msg, toSend := make([]byte, 256), 100
+	rand.Read(msg)
+
+	for i := 0; i < toSend; i++ {
+		if _, err = js.Publish("foo", msg); err != nil {
+			t.Fatalf("Unexpected publish error: %v", err)
+		}
+	}
+
+	sub, err := js.SubscribeSync("foo")
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	checkSubsPending(t, sub, toSend)
+	ci, err := sub.ConsumerInfo()
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if ci.NumAckPending != toSend {
+		t.Fatalf("Expected %d to be pending, got %d", toSend, ci.NumAckPending)
+	}
+
+	// Wait for messages to expire.
+	checkFor(t, 2*time.Second, 100*time.Millisecond, func() error {
+		si, err := js.StreamInfo("TEST")
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+		if si.State.Msgs != 0 {
+			return fmt.Errorf("Expected 0 msgs, got state: %+v", si.State)
+		}
+		return nil
+	})
+
+	// Once expired these messages can not be redelivered so should not be considered ack pending at this point.
+	// Now ack..
+	ci, err = sub.ConsumerInfo()
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if ci.NumAckPending != 0 {
+		t.Fatalf("Expected nothing to be ack pending, got %d", ci.NumAckPending)
+	}
+}
+
+func TestJetStreamClusterAckPendingWithMaxRedelivered(t *testing.T) {
+	c := createJetStreamClusterExplicit(t, "R3", 3)
+	defer c.shutdown()
+
+	// Client based API
+	nc, js := jsClientConnect(t, c.randomServer())
+	defer nc.Close()
+
+	_, err := js.AddStream(&nats.StreamConfig{
+		Name:     "TEST",
+		Subjects: []string{"foo", "bar"},
+		Replicas: 3,
+	})
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	// Send in 100 messages.
+	msg, toSend := make([]byte, 32), 100
+	rand.Read(msg)
+
+	for i := 0; i < toSend; i++ {
+		if _, err = js.Publish("foo", msg); err != nil {
+			t.Fatalf("Unexpected publish error: %v", err)
+		}
+	}
+
+	sub, err := js.SubscribeSync("foo",
+		nats.MaxDeliver(2),
+		nats.Durable("dlc"),
+		nats.AckWait(10*time.Millisecond),
+		nats.MaxAckPending(10),
+	)
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	checkSubsPending(t, sub, toSend*2)
+	ci, err := sub.ConsumerInfo()
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if ci.NumAckPending != 0 {
+		t.Fatalf("Expected nothing to be ack pending, got %d", ci.NumAckPending)
+	}
+}
+
 // Support functions
 
 // Used to setup superclusters for tests.